A comparative study of the pigments in microbial fractions from the sheep's rumen and in the corresponding diet

In microbial fractions separated from the rumen contents of a hay‐fed sheep pigmentation was found to be caused by pigments normally associated with plant chloroplasts. The extent of this pigmentation was greater than might be expected from the concentration in the hay feed. No chlorophyll typical of the known pigmented bacteria was found. An assessment of plant‐particle contamination of microbial fractions, based on the pigment concentrations found, agreed in general with an assessment by a new direct‐observation technique. The lowest contamination found was calculated to be of the order of 10%. Degradation of chlorophylls in the rumen was demonstrated and was found to be more extensive when artificially dried grass was fed than when hay was fed. The implications of these findings are discussed.